Geodetic Instruments Research Articles

Spatial Variations of Aftershock Parameters and their Relation to Geodetic Slip Models for the 2010 Mw8.8 Maule and the 2011 Mw9.0 Tohoku-oki Earthquakes

Recent development in analysis tools and deployments of the geodetic and seismic instruments give an opportunity to investigate aftershock sequences at local scales, which is important for the seismic hazard assessment. In particular, we study the dependencies between aftershock sequences properties and deformational/geological data on a scale of the rupture extension of megathrust earthquakes. For this goal we use, on one hand, published models of inter-, co- and postseismic slip and geological information and, on the other hand, aftershock parameters, obtained by fitting a modified Epidemic Type Aftershock Sequence (ETAS) model. The altered ETAS model takes into account the mainshock rupture extension and it distinguishes between primary and the secondary aftershock triggering involved in the total seismicity rate. We estimate the Spearman correlation coefficients between the spatially distributed aftershock parameters estimated by the modified ETAS model and crustal physical properties for the Maule 2010 Mw8.8 and the Tohoku-oki 2011 Mw9.0 aftershock sequences. We find that: (1) modified ETAS model outperforms the classical one, when the mainshock rupture extension cannot be neglected and represented as a point source; (2) anomalous aftershock parameters occur in the areas of the reactivated fault systems; (3) aftershocks, regardless of their generation, tend to occur in the areas of high coseismic slip gradient, afterslip and interseismic coupling; (4) aftershock seismic moment releases preferentially in regions of large coseismic slip, coseismic slip gradient and interseismically locked areas; (5) b value tends to be smaller in interseismically locked regions.

Validation of GPS-IR Soil Moisture Retrievals: Comparison of Different Algorithms to Remove Vegetation Effects

The GPS interferometric reflectometry (GPS-IR) technique can be used to estimate near-surface soil moisture from signal-to-noise ratio (SNR) data collected with standard geodetic instrumentation. However, the effects of vegetation on GPS-IR soil moisture retrievals must be considered in some environments. In situ soil moisture observations from 11 GPS sites are used to compare the performance of three different retrieval algorithms that represent vegetation effects with different degrees of complexity. A bare-soil retrieval algorithm does not perform well, even at sites where seasonal variations in vegetation water content (VWC) are less than 1 kg m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . The range of volumetric soil moisture (VSM) is too large due to the effects of vegetation on phase of the SNR interferogram, yielding an RMSE between in situ and GPS-IR VSM of 0.055 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Errors are reduced by an algorithm that adjusts for vegetation effects using variations in the amplitude of the SNR interferogram. RMSE is 0.038 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> using this algorithm, below the typical limit required for validation of satellite data. This simple vegetation algorithm performs poorly at sites where seasonal variations in VWC are 1 kg m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> or greater. A more complex algorithm, that uses amplitude in conjunction with frequency analysis of the SNR interferogeram to predict vegetation effects, provides acceptable performance at these sites ( RMSE = 0.039 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> ). The additional complexity of this algorithm is only warranted at sites where the simple vegetation algorithm cannot adequately represent the effects of the vegetation fluctuations.

Footprints of past earthquakes revealed in the afterslip of the 2010 Mw 7.8 Mentawai tsunami earthquake

AbstractThe 2010 Mw 7.8 Mentawai tsunami earthquake marks one of the first tsunami earthquakes to have postseismic deformation observed by geodetic instruments. The Sumatran GPS Array has recorded the postseismic deformation following this event continuously for &gt;5 years. The spatiotemporal evolution of the postseismic deformation is well explained by velocity‐strengthening frictional sliding on the Sunda megathrust. Our results show that the 2010 afterslip progressed downdip relative to the 2010 coseismic rupture. The southeastern portion of the afterslip region overlaps the area that slipped during the main shock and afterslip of the 2007 Mw 8.4 Bengkulu earthquake, while the northwestern portion slipped an area without recent large earthquakes. By incorporating pre‐earthquake stress conditions into quasi‐dynamic models, we demonstrate that the preceding cumulative slip from the 2007 sequence might have caused a ∼0.1 MPa difference in pre‐earthquake Coulomb stress between the southeastern and northwestern portions of the afterslip region.

Digital astro-geodetic camera system for the measurement of the deflections of the vertical: tests and results

ABSTRACTThis study introduces the new results of a novel low-cost digital zenith camera system operated in Turkey that uses astronomical and geodetic instrumentation. Currently, it is possible to determine deflections of the vertical (DoV) components by using a vast amount of information gathered from geo-referenced star images, tilt measurements, and Global Navigation Satellite System technology. This new design of an astro-geodetic camera system is used for calculating DoV components with 12 independent solutions on a test station in Istanbul, and additional observations were performed to investigate the external accuracy of the system on a test network. A specific leveling method is developed to align system toward the zenithal direction. The final results of the observations on a test station located in Istanbul indicate that the accuracy of the system is about ±0.19 arc-seconds in latitude and ±0.28 arc-seconds in longitude determination. The system has been further tested on a network with 4 control points that have averagely 20 km baselines. At the test network, the root mean square of the average value of the vertical deflections is calculated as ±0.36 arc-seconds. Furthermore, DoV components are compared with the values that are calculated using global geopotential models.

Dinamika dan Evolusi Pantai Probolinggo, Jawa Timur

&lt;strong&gt;Dynamics and Evolution of the Coast of Probolinggo, East Java.&lt;/strong&gt; The coastal plain of Probolinggo extends from Tongas Subdistrict in the western part to Kraksaan Subdistrict in the eastern part. The south side is the fertile rice field area, while the north side is the fish pond area. The phenomena of coastal changes in Probolinggo are strongly influenced by the materials supplied from Mount Bromo. This research was conducted in April–May 2012, February 2013, and August 2014 and aimed to gain insight into the coastal dynamics and evolution as well as changes and land cover convertion in Probolinggo. The analysis of coastal changes in Probolinggo from 1973 until 2013 was done using multitemporal landsat imageries, the measurement and drawing of coastal profile were carried out using shokiza geodetic instrument and SeaBird Electronic tide gauge. The results showed that in the western part, the accretion process is still ongoing, while in the eastern part, the accretion speed since 1989 has continued to decline and even some places experienced erosion. The new coastal plain formed by the accretion of marine processes is utilized by the residents as fish ponds, whereas accretion formed by fluvial processes is utilized as rice fields. &lt;br /&gt;&lt;br /&gt;

Local tsunami warnings: Perspectives from recent large events

AbstractWe demonstrate a flexible strategy for local tsunami warning that relies on regional geodetic and seismic stations. Through retrospective analysis of four recent tsunamigenic events in Japan and Chile, we show that rapid earthquake source information, provided by methodologies developed for earthquake early warning, can be used to generate timely estimates of maximum expected tsunami amplitude with enough accuracy for tsunami warning. We validate the technique by comparing to detailed models of earthquake source and tsunami propagation as well as field surveys of tsunami inundation. Our approach does not require deployment of new geodetic and seismic instrumentation in many subduction zones and could be implemented rapidly by national monitoring and warning agencies. We illustrate the potential impact of our method with a detailed comparison to the actual timeline of events during the recent 2015 Mw8.3 Illapel, Chile, earthquake and tsunami that prompted the evacuation of 1 million people.

The Comparison of Measuring and Computing Results of Construction Vertical Displacement

The paper presents the methods for controlling vertical displacements on a reinforced concrete slab. To take the measurements we used geodetic instruments (level, total station and laser level) as well as non-geodetic instruments (inductive transducers). Theoretic displacements at the crack are calculated in accordance with European regulations for reinforced and pre-stressed concrete. Many objects or constructions must be tested before applied. For many years on Faculty of Civil Engineering, Maribor, Slovenia, are performed structures loading tests for analysis of materials.

Analysis of Precision of Geodetic Instruments for Investigating Vertical Displacement of Structures

This paper presents the analysis of preciseness and safety of different instruments for researching the vertical displacements of the objects in the space. In Slovenia researching the objects by the test of pressure is obligatory for all structures, which are longer than 15 meters (JUS U.M1.046). Among all the methods we choose geodetic as well as non-geodetic ones. There are many methods for researching the displacements, so we took limits to the instruments available to us. On the Faculty of Civil Engineering, University of Maribor, Slovenia, used the level, total station, and inductive transducer and laser level. The measures of displacements were made on the reinforced concrete plate, type PVP5. For the plate we calculated the foreseen displacements by the analytic as well as by the numeric method. For analytic calculation we used the national regulations (Euro code 2) and for numeric part we used the programme Ocean. For each instrument we calculated the standard deviation and the optimal accuracy, we checked the significance of results by the analysis of variances with one variable factor. In this paper we described all the instruments for following the displacements and the working principles of instruments by which the research was made and the measurement errors. The analysis of precise was made on the base of comparation between the results of foreseen displacements and the gained results of measurements. The results of this research are gathered in a conclusion and give us the answer to the goals.

Fusion of range-based data and image-based datasets for efficient documentation of cultural heritage objects and sites

Abstract. Nowadays it is possible to measure accurately dense point clouds either with aerial/terrestrial laser scanning systems or with imagebased solutions (namely based on photogrammetric computer vision algorithms such as structure-from-motion (SfM)), from which highly detailed 3D models can be achieved. Besides, direct tools in the form of simple devices such as rulers, compass and plumblines are usually required in simple metric surveys, as well as high-end surveying and geodetic instruments such as robotized imagebased total stations and GNSS (probably to a lesser degree but still required) to set the archaeological/architectural recording project in a global reference frame. With all this gamut of image-based and range-based sensors and datasets (in the form of coordinates, point clouds or 3D models), in different coordinate systems (most of the times local for each device), lack of uniform scale, orientation and levelling, the fusion of data tends to be cumbersome. This paper presents an efficient way to fuse and merge different datasets in the form of point clouds/3D models and geodetic/UTM coordinates. The new developed 3DVEM – Register GEO software is able to handle datasets coming from both direct and indirect methods in order to provide unified and precise deliverables.

Determining the inclination of tall chimneys using the TPS and TLS approach

In order to ensure safe operation of tall industrial chimneys their verticality needs to be accurately monitored. Vertical plumbing, the classic geodetic procedure for detecting the inclination has certain drawbacks and can be replaced by modern technology if necessary. In this article we are going to propose a more general and rigorous procedure, which includes measurements that result in point clouds, and explain the processing of this type of data. In our case study we used two types of modern geodetic instruments: the most accurate total station (TPS) Leica TS30 and the terrestrial laser scanner (TLS) Riegl VZ-400. Data acquired with these instruments were fit to a cylinder using the least squares adjustment and the results were compared. The article points out the differences between the used technologies as well as the differences between the results. During the study certain questions arose and we tried our best to explain and solve them. These included: the outlier detection and removal, the influence of large amounts of data on processing time and accuracy estimates, the influence of angle of incidence of laser beam on the chimney’s inclination. In the end the deviations from the best fitting model were investigated. The article represents a comprehensive review of the use of modern geodetic technology for solving important engineering monitoring tasks.

Evaluation of a pulsed terrestrial laser scanner based on ISO standards

The evaluation of the accuracy and precision of measuring equipment is critical in order to achieve results that meet the specifications of a given project. Standard calibration models and field procedures exist for all traditional surveying instruments, but are still lacking for recently developed technologies like terrestrial laser scanners (TLS). The main reason is limited knowledge of errors that affect these systems, owing to the proprietary design of the scanners and their software, and the integration of many potential sources of error. Owing to the difficulty of separating the different error sources of TLS, it is proposed in this paper that a test procedure can assess the overall achievable precision for a scanner instrument without individual errors being known. The proposed tests are based on the International Organization for Standardization specifications for geodetic instruments (www.iso.org). The tests can be performed in either a controlled or uncontrolled environment, which is advantageous for on-the-job calibration. A pulsed terrestrial laser scanner (Leica Scanstation 2) was used as a test subject and the evaluation results indicated that the specific instrument performed well within the manufacturer’s specifications.

Online system for monitoring the safety of engineering structures

Original scientific paper Monitoring engineering structures is a very important issue for the safety of these structures. Maintaining the safety of engineering structures depends on determining the possible deformations to the structures and taking the necessary precautions in time. In this instance, monitoring the structures became a very important problem. In this study, a prototype of web-based online monitoring system design and implementation was carried out for monitoring the movements of Fatih Sultan Mehmet Bridge which was one of Istanbul’s suspended bridges. Raw observations taken by geodetic instruments can be filtered by different filtering techniques and can be analyzed by trend and FFT analysis methods. With the help of these techniques, overall monitoring of the structure was possible. Designed monitoring system can be used on different types of engineering structures such as skyscrapers and dams. With the help of this online monitoring system, project managers or any other officials, in the office, can see the observations in real time and can analyze the results while operators are working near the structure.

Development of Calibration Equipment for Geodetic Angle Measurement Instruments

Production of high precision circular scales is a complicated process requiring expensive equipment and complex processes to achieve. Precision angle measurement equipment tends to be very expensive and therefore not accessible to all in need. Simplification of production of such devices can lead to reducing costs of angle measurement systems ensuring easier accessibility. A new method of producing precision circular scales using low cost mass production can reduce the costs of these devices drastically. Therefore, utilising a common CD technology as the basis for such scales is analysed. This paper deals with the analysis of the newest laser cutting method for plastic circular scales. Preliminary results of manufacturing such scales are presented in the paper as well as measurements of the grating of the scale were performed. The quality of different scales manufactured using different laser types is analysed in the study. The cost – effective alternative of manufacturing circular scales is discussed in the paper.

Investigation of Systematic Errors for the Hybrid and Panoramic Scanners

The existence of terrestrial laser scanners (TLSs) with capability to provide dense three-dimensional (3D) data in short period of time has made it widely used for the many purposes such as documentation, management and analysis. However, similar to other sensors, data obtained from TLSs also can be impaired by errors coming from different sources. Then, calibration routine is crucial for the TLSs to ensure the quality of the data. Through self-calibration, this study has performed system calibration for hybrid (Leica ScanStation C10) and panoramic (Faro Photon 120) scanner at the laboratory with dimensions 15.5m x 9m x 3m and more than hundred planar targets that were fairly distributed. Four most significant parameters are derived from well-known error sources of geodetic instruments as constant (a0), collimation axis (b0), trunnion axis (b1) and vertical circle index (c0) errors. Data obtained from seven scan-stations were processed, and statistical analysis (e.g. t-test) has shown significant errors for the calibrated scanners.

Earth and space observation at the German Antarctic Receiving Station O’Higgins

ABSTRACTThe German Antarctic Receiving Station (GARS) O’Higgins at the northern tip of the Antarctic Peninsula is a dual purpose facility for earth observation and has existed for more than 20 years. It serves as a satellite ground station for payload data downlink and telecommanding of remote sensing satellites as well as a geodetic observatory for global reference systems and global change. Both applications use the same 9 m diameter radio antenna. Major outcomes of this usage are summarised in this paper.The satellite ground station O’Higgins (OHG) is part of the global ground station network of the German Remote Sensing Data Centre (DFD) operated by the German Aerospace Centre (DLR). It was established in 1991 to provide remote sensing data downlink support within the missions of the European Remote Sensing Satellites ERS-1 and ERS-2. These missions provided valuable insights into the changes of the Antarctic ice shield. Especially after the failure of the on-board data recorder, OHG became an essential downlink station for ERS-2 real-time data transmission. Since 2010, OHG is manned during the entire year, specifically to support the TanDEM-X mission. OHG is a main dump station for payload data, monitoring and telecommanding of the German TerraSAR-X and TanDEM-X satellites.For space geodesy and astrometry the radio antenna O’Higgins significantly improves coverage over the southern hemisphere and plays an essential role within the global Very Long Baseline Interferometry (VLBI) network. In particular the determination of the Earth Orientation Parameters (EOP) and the sky coverage of the International Celestial Reference Frame (ICRF) benefit from the location at a high southern latitude. Further, the resolution of VLBI images of active galactic nuclei (AGN), cosmic radio sources defining the ICRF, improves significantly when O’Higgins is included in the network. The various geodetic instrumentation and the long time series at O’Higgins allow a reliable determination of crustal motions. VLBI station velocities, continuous GNSS measurements and campaign-wise absolute gravity measurements consistently document a vertical rate of about 5 mm/a. This crustal uplift is interpreted as an elastic rebound due to ice loss as a consequence of the ice shelf disintegration in the Prince Gustav Channel in the late 1990s.The outstanding location on the Antarctic continent and its year-around operation make GARS O’Higgins in future increasingly attractive for polar orbiting satellite missions and a vitally important station for the global VLBI network. Future plans call for the development of an observatory for environmentally relevant research. That means that the portfolio of the station will be expanded including the expansion of the infrastructure and the construction and operation of new scientific instruments suitable for long-term measurements and satellite ground truthing.

Increasing of the accuracy of vertical angle measurements of geodetic instrumentation

There is a vast number of geodetic angle meas-urement equipment (like techeometers, theodolites, laser scanners etc.) implemented in the geodesy, civil engineer-ing, construction engineering etc. The accuracy of meas-urement of mentioned equipment directly influence the quality of buildings, private state measures etc. Though there is a methodology of testing of such equipment offi-cially adopted, such methodology allows determination of solely random errors of measurements at several angular positions of the instrument. The accuracy (random errors and biases) is still unknown for huge part of the angular values generated by the instrument while measurements. In the paper the theoretical assumptions on possible increasing the measurements accuracy by means of precise calibration in a bigger range of possible measurements is described together with some examples of practical solution of the problem. DOI: http://dx.doi.org/10.5755/j01.mech.20.4.7884

Tsunami Modeling, Fluid Load Simulation, and Validation Using Geospatial Field Data

AbstractThis paper presents an integrated, interdisciplinary methodology incorporating multiphysics, multiscale numerical modeling and simulation from tsunami generation, propagation, and inundation to subsequent coupled structural response and associated fluid loads. This novel, cohesive approach performs these simulations across a large spectrum of scales, enabling structural engineers to take full advantage of the detail available in recent advances in tsunami modeling, geospatial data collection, and computational structural mechanics. Extensive seismic networks, geodetic instruments, and water-level stations provide unprecedented data sets, enabling one to model, simulate and reconstruct tsunami events with high fidelity. A number of coordinated, ground-based surveys also collect valuable, time-sensitive quantitative information to improve understanding of structural response to tsunami loading following events. Recently, some of these surveys include high-resolution LIDAR measurements, which provide...

Theoretical aspects of the calibration of geodetic angle measurement instrumentation

There are multiple instruments directly imple-menting the principle of angle measurements (horizontal and vertical) for its functioning, used in geodesy, surveying and machine building (like tacheometers, theodolites, laser scanners, laser trackers etc.). As for the moment, there is no official reglamentation regarding calibration and testing of such instrumentation in entire range of the measurements, though instrumentation produce a huge number of both horizontal and vertical angular values during its normal implementation. In the paper the theoretical assumptions of such instrumentation testing and calibration together with examples of some practical tests are given. DOI: http://dx.doi.org/10.5755/j01.mech.20.1.6590

Comparison of Site Velocities Derived from Collocated GPS, VLBI and SLR Techniques at The Hartebeesthoek Radio Astronomy Observatory (Comparison of Site Velocities)

Abstract Space geodetic techniques provide highly accurate methods for estimating bedrock stability at subcentimetre level. We utilize data derived from Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI) and Global Positioning Systems (GPS) techniques, collocated at the Hartebeesthoek Radio Astronomy Observatory, to characterise local plate motion and compare the solutions from the three techniques. Data from the GNSS station were processed using the GAMIT/GLOBK (version 10.4) software, data from the SLR station (MOBLAS-6)were processed using the Satellite Laser Ranging Data Analysis Software (SDAS) and the VLBI data sets were processed using the Vienna VLBI Software (VieVS) software. Results show that there is a good agreement between horizontal and vertical velocity components with a maximum deviation of 1.7 mm/yr, 0.7 mm/yr and 1.3 mm/yr between the North, East and Up velocity components respectively for the different techniques. At HartRAO there is no significant trend in the vertical component and all the techniques used are consistent with the a-priori velocities when compared with each other. This information is crucial in monitoring the local motion variations since geodetic instruments require a very stable base to minimise measurement errors. These findings demonstrate that station coordinate time-series derived with different techniques and analysis strategies provide comparable results.

Determination of Geometrical Track Position by Robotic Total Station

Robotic total stations belongs to the most innovative and advanced geodetic instruments used in engineering practice with the performance to maximize productivity and to accomplish requirements concerning to the high angle and distance precision. Robotic Total Station Trimble S8 was used for precise terrestrial measurements of railway track built on ballast-less track construction to diagnose the track behaviour under traffic loading.